UF study raises question of how best to increase Vitamin D intake

Published: Tuesday, January 22, 2013 at 6:36 p.m.

Last Modified: Tuesday, January 22, 2013 at 6:36 p.m.

GAINESVILLE - The benefits of taking vitamin D are still up for discussion: Known to be good for bone health, the jury is still out on its ability to protect against certain types of cancer, heart disease and even depression.

A recent study from the University of Florida shows that vitamin D also might have a role in reducing health disparities. It found that vitamin D deficiency might be a risk factor for increased knee osteoarthritis pain in African-Americans, who generally have lower vitamin D levels because their skin absorbs less sunlight, a natural source of vitamin D.

"If additional research demonstrates that improving vitamin D status lessens knee osteoarthritis pain, identifying and treating vitamin D deficiency may improve function for older adults with osteoarthritis and reduce health disparities for black Americans," the study, which was published in the December issue of Arthritis and Rheumatism, concluded.

Specifically, the study found that African-Americans had greater sensitivity to heat and pressure-induced pain. They also had greater initial perception of pain, which led researchers to conclude that vitamin D levels are related to the pain pathways involved in the onset of pain. Cells in the peripheral and central nervous system contain vitamin D receptors.

One of the authors of the study, Toni Glover, a research nurse practitioner and certified pain educator at UF, said more research is needed to confirm these findings. Meanwhile, the study concluded that "improving vitamin D status is inexpensive and with low risk of adverse events."

"People should really know what their level is," Glover added.

While it's true that vitamin D supplements might not cost much (100 tablets cost less than $10), the lab test to screen for vitamin D levels costs about $200, and that can sometimes be a barrier to more people getting screened, especially since insurance often doesn't cover it, said Dr. Robert Fields, a family medicine practitioner at Shands' Family Medicine at Main.

Meanwhile, studies have shown that vitamin D levels are dropping in the general population.

"More and more of the population is rightly avoiding direct sunlight exposure for long periods, so we are making less vitamin D," Fields said.

That's especially worrisome for certain parts of the population, he added.

"We preach (the need for sufficient vitamin D intake) to our teens, pregnant women and mothers through the baby's first year of life," Fields said, adding that teens often are deficient because they don't drink enough milk, which is fortified with vitamin D.

Fields added that the American Academy of Pediatrics for the past few years has recommended supplementing all infants with vitamin D since it is critical for bone growth. Obese mothers should make sure they have high enough levels of vitamin D since obese people store more vitamin D in their fat cells, where it is more resistant to being pulled out — and obese mothers can pass on a vitamin D deficiency to their offspring, said Dr. Wendy Dahl, assistant professor in Food Science and Human Nutrition at UF.

In the elderly, vitamin D helps maintain bone mineral density, Dahl said, adding that they are especially at risk of vitamin D deficiency because "there's less of the sun exposure activation with age."

But everyone is susceptible to deficient levels of vitamin D, Dahl continued. A study of UF students she conducted found that 30 percent had insufficient levels of vitamin D. Dermatologists' recommendation to stay out of the sun because of skin cancer risk has meant that people's natural intake of vitamin D through sunlight exposure can't be counted on, and skin tan lotions with as low as 15 SPF block out the ultraviolet rays responsible for vitamin D synthesis, Dahl said.

However, "most Americans have adequate levels for bone health," Dahl said, adding that many foods are vitamin D-fortified, and the FDA just approved increased levels of fortification for breads and cereals.

"If all the breads and cereals had the actual fortification, we wouldn't have any problem with intake — the majority of us would have enough," Dahl said, adding, "We don't have major issues with other vitamin deficiencies in the country."

Salmon and sardines are considered to be the best food sources of vitamin D.